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Carbohydrate response element-binding protein (ChREBP) plays a pivotal role in beta cell glucotoxicity.

ABSTRACT: This study was aimed at the elucidation of the pathogenesis of glucotoxicity, i.e. the mechanism whereby hyperglycaemia damages pancreatic beta cells. The identification of pathways in the process may help identify targets for beta cell-protective therapy. Carbohydrate response element-binding protein (ChREBP), a transcription factor that regulates the expression of multiple hyperglycaemia-induced genes, is produced in abundance in pancreatic beta cells. We hypothesise that ChREBP plays a pivotal role in mediating beta cell glucotoxicity.We assessed the role of ChREBP in glucotoxicity in 832/13 beta cells, isolated mouse islets and human pancreas tissue sections using multiple complementary approaches under control and high-glucose-challenge conditions as well as in adeno-associated virus-induced beta cell-specific overexpression of Chrebp (also known as Mlxipl) in mice.Under both in vitro and in vivo conditions, ChREBP activates downstream target genes, including fatty acid synthase and thioredoxin-interacting protein, leading to lipid accumulation, increased oxidative stress, reduced insulin gene transcription/secretion and enhanced caspase activity and apoptosis, processes that collectively define glucotoxicity. Immunoreactive ChREBP is enriched in the nucleuses of beta cells in pancreatic tissue sections from diabetic individuals compared with non-diabetic individuals. Finally, we demonstrate that induced beta cell-specific Chrebp overexpression is sufficient to phenocopy the glucotoxicity manifestations of hyperglycaemia in mice in vivo.These data indicate that ChREBP is a key transcription factor that mediates many of the hyperglycaemia-induced activations in a gene expression programme that underlies beta cell glucotoxicity at the molecular, cellular and whole animal levels.

SUBMITTER: Poungvarin N

PROVIDER: S-EPMC4010252 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Carbohydrate response element-binding protein (ChREBP) plays a pivotal role in beta cell glucotoxicity.

Poungvarin N N Lee J K JK Yechoor V K VK Li M V MV Assavapokee T T Suksaranjit P P Thepsongwajja J J JJ Saha P K PK Oka K K Chan L L

Diabetologia 20120303 6

<h4>Aims/hypothesis</h4>This study was aimed at the elucidation of the pathogenesis of glucotoxicity, i.e. the mechanism whereby hyperglycaemia damages pancreatic beta cells. The identification of pathways in the process may help identify targets for beta cell-protective therapy. Carbohydrate response element-binding protein (ChREBP), a transcription factor that regulates the expression of multiple hyperglycaemia-induced genes, is produced in abundance in pancreatic beta cells. We hypothesise th ...[more]

PMID: 22382520

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Project description:ObjectiveCarbohydrate response element binding protein (ChREBP) is a transcription factor that responds to glucose and activates genes involved in the glycolytic and lipogenic pathways. Recent studies have linked adipose ChREBP to insulin sensitivity in mice. However, while ChREBP is most highly expressed in the liver, the effect of hepatic ChREBP on insulin sensitivity remains unknown. To clarify the importance of hepatic ChREBP on glucose homeostasis, we have generated a knockout mouse model that lacks this protein specifically in the liver (Liver-ChREBP KO).MethodsUsing Liver-ChREBP KO mice, we investigated whether hepatic ChREBP deletion influences insulin sensitivity, glucose homeostasis and the development of hepatic steatosis utilizing various dietary stressors. Furthermore, we determined gene expression changes in response to fasted and fed states in liver, white, and brown adipose tissues.ResultsLiver-ChREBP KO mice had impaired insulin sensitivity as indicated by reduced glucose infusion to maintain euglycemia during hyperinsulinemic-euglycemic clamps on both chow (25% lower) and high-fat diet (33% lower) (p < 0.05). This corresponded with attenuated suppression of hepatic glucose production. Although Liver-ChREBP KO mice were protected against carbohydrate-induced hepatic steatosis, they displayed worsened glucose tolerance. Liver-ChREBP KO mice did not show the expected gene expression changes in liver in response to fasted and fed states. Interestingly, hepatic ChREBP deletion also resulted in gene expression changes in white and brown adipose tissues, suggesting inter-tissue communication. This included an almost complete abolition of BAT ChREBPβ induction in the fed state (0.15-fold) (p = 0.015) along with reduced lipogenic genes. In contrast, WAT showed inappropriate increases in lipogenic genes in the fasted state along with increased PEPCK1 in both fasted (3.4-fold) and fed (5.1-fold) states (p < 0.0001).ConclusionsOverall, hepatic ChREBP is protective in regards to hepatic insulin sensitivity and whole body glucose homeostasis. Hepatic ChREBP action can influence other peripheral tissues and is likely essential in coordinating the body's response to different feeding states.

Project description:The intracellular lipids in muscle cells of farm animals play a crucial role in determining the overall intramuscular fat (IMF) content, which has a positive impact on meat quality. However, the mechanisms underlying the deposition of lipids in muscle cells of farm animals are not yet fully understood. The purpose of this study was to determine the roles of carbohydrate-response element binding protein (ChREBP) and fructose in IMF deposition of chickens. For virus-mediated ChREBP overexpression in tibialis anterior (TA) muscle of chickens, seven 5-d-old male yellow-feather chickens were used. At 10 d after virus injection, the chickens were slaughtered to obtain TA muscles for analysis. For fructose administration trial, sixty 9-wk-old male yellow-feather chickens were randomly divided into 2 groups, with 6 replicates per group and 5 chickens per replicate. The chickens were fed either a basal diet or a basal diet supplemented with 10% fructose (purity ≥ 99%). At 4 wk later, the chickens were slaughtered, and breast and thigh muscles were collected for analysis. The results showed that the skeletal ChREBP mRNA levels were positively associated with IMF content in multiple species, including the chickens, pigs, and mice (P < 0.05). ChREBP overexpression increased lipid accumulation in both muscle cells in vitro and the TA muscles of mice and chickens in vivo (P < 0.05), by activation of the de novo lipogenesis (DNL) pathway. Moreover, activation of ChREBP by dietary fructose administration also resulted in increased IMF content in mice and notably chickens (P < 0.05). Furthermore, the lipidomics analysis revealed that ChREBP activation altered the lipid composition of chicken IMF and tented to improve the flavor profile of the meat. In conclusion, this study found that ChREBP plays a pivotal role in mediating the deposition of fat in chicken muscles in response to fructose-rich diets, which provides a novel strategy for improving meat quality in the livestock industry.

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Carbohydrate response element-binding protein (ChREBP) plays a pivotal role in beta cell glucotoxicity.

Publications

Carbohydrate response element-binding protein (ChREBP) plays a pivotal role in beta cell glucotoxicity.

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